Bug 23355: (RM follow-up) Make DB update idempotent

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>

installer/data/mysql/updatedatabase.pl

@@ -21274,14 +21274,14 @@ if( CheckVersion( $DBversion ) ) {
 $DBversion = '19.12.00.054';
 if( CheckVersion( $DBversion ) ) {
     $dbh->do(qq{
-             CREATE TABLE desks ( -- desks available in a library
-             desk_id int(11) NOT NULL auto_increment, -- unique identifier added by Koha
-             desk_name varchar(100) NOT NULL default '', -- name of the desk
-             branchcode varchar(10) NOT NULL,       -- library the desk is located at
-             PRIMARY KEY  (desk_id),
-             KEY `fk_desks_branchcode` (branchcode),
-             CONSTRAINT `fk_desks_branchcode` FOREIGN KEY (branchcode) REFERENCES branches (branchcode) ON DELETE CASCADE ON UPDATE CASCADE
-             ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+         CREATE TABLE IF NOT EXISTS `desks` ( -- desks available in a library
+           `desk_id` int(11) NOT NULL auto_increment, -- unique identifier added by Koha
+           `desk_name` varchar(100) NOT NULL default '', -- name of the desk
+           `branchcode` varchar(10) NOT NULL,       -- library the desk is located at
+           PRIMARY KEY (`desk_id`),
+           KEY `fk_desks_branchcode` (`branchcode`),
+           CONSTRAINT `fk_desks_branchcode` FOREIGN KEY (`branchcode`) REFERENCES `branches` (`branchcode`) ON DELETE CASCADE ON UPDATE CASCADE
+         ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
     });
 
     NewVersion( $DBversion, 13881, "Add desk management");